The present invention relates to transferring light from a light guide to an end use, and more particularly in regulating the transfer of light with low loss.
It is generally known in the art to regulate transfer of light from a first light guide comprised of one or more optical fibers to a desired end use. Typically, an associated, high efficiency light source provides light to an input end of an optical fiber system which, in turn, transmits the light to the desired end use. For selected applications, regulation or interruption of the light flow through the light guide is necessary. For example, the application may require rapid on and off states, or alternatively, the amount of light passing through the light guide requires regulation. Rather than regulating the light at the source, as is typical, it may be more desirable to maintain the light source in an on state and selectively interrupt light flow at a remote location in the optical fiber path.
There are various known methods for switching light on and off in systems using light guides. For example, a mechanical interruption such as a mechanical shutter may be provided at the input end of the light guide. This is often undesirable since design requirements do not always accommodate such a structure adjacent the light source.
According to another arrangement, a liquid crystal display panel (LCD) is disposed between a pair of lenses whereby light exiting the first light guide is collimated, passes through the LCD, and is then focused by the second lens onto the input end of a second light guide. By regulating an electrical field associated with the LCD, electrical dipole axes of the liquid crystal molecules are selectively aligned to provide a dynamic regulation of light transmissibility. This type of arrangement provides an on/off ratio of light transmission on the order of approximately 30:1. One problem associated with this arrangement is the loss associated with scattering as the light proceeds from the output end of the first light guide, through the collimating lens, through the scattering panel, through a focusing lens, and into the input end of the second light guide. Even if careful consideration is given to the various materials, losses result due to scattering. It is thus important to minimize these losses so that an increased ratio between on and off states can be achieved.
One particular use for such an arrangement is in the automobile industry where, for example, an increased emphasis is placed on a central light source and use of a fiber optic system to conduct the light to remote locations for various applications, such as tail lights, interior lighting, display panel, etc. Such a centralized system substantially precludes regulation of light by turning the light source on and off, or regulating the light at the input end of the fiber optic system, i.e., at the light source.